I'm dialing in the carbs on a engine. The engine is a used engine that had a bit of waterdamage from sitting unused, outside. The bearings, bores, etc looked OK so I only checked the torque settings on all the nuts & bolts ( to make sure, because I could see somebody had been inside this engine ) And I lapped the valves. The valves & seats were not great, but I think ( thought ) I got them to seal. Right now, the symptoms are: I'm measuring a richer mixture that I should with the jets I'm using ( going off a list I have with this particular engine ( 4cyl) and carbs ( 40 DCOE's ) And one of the pipes on the header measures a lower temp than the rest ( about 300deg compared to the 550 to 600 of the rest ) And if I pull the wire off the plug on that cyl, the RPM drops the least. Electrical? It has a used Mallory dual point with new points, cap, rotor, condensor, and new plugs but used wires. Compression? I did a compression test and they all measured the same ( low, but the same ) But Im not sure I trust the Compression tester. Thanks... So going by these Symptoms, what would be the problem, most likely?
Hold the wire and make the spark jump to the plug, it intensifies the spark. See if it runs smoother. I've found weak plug or wires this way.
Swap spark plugs and wires if the miss stays the same move on. If you find yourself completely stumped do a cylinder leak-down test. This will eliminate guessing >>>>.
Thanks guys. I think I'll be chasing this one for a while, because there is nothing really obvious. ( the header tube temps are now the same, but no difference in the wideband readings or performance.) I played with diferent jets today, used another cap ( also new ), switched wires and plugs, and re-adjusted the valve lash. I dont think its a full on miss, I think I'd hear it and I think it would vibrate more ( solid mounted engine ) My plan is now to put the wideband on another car, of which I know what the mixture should read, to check the machine. And see if I can get a leakdown done on my engine.
Not knowing what kind of engine it is, does it have an egr valve that could be stuck? That would affect one cylinder and be hard to detect.
No, I dont think there is a vacuum leak. It has Pierce manifolds' soft mounts on it. They are new and in good shape. The intake manifold looks like its in good shape ( I did weld up a spot that looked rough, just incase it would be porous in that spot ) The carbs have not been on a car in about 20 years, but I cleaned them and replaced gaskets etc before I started the engine. I'm using the right ( filterking ) filter/press regulator ( same age as the carbs, but also rebuilt with a new membrane )
No emissions equipment at all. Just a breather with a baffle and a filter connected to the crank case and the valve cover. No vacuum take off for powerbrakes or anything like that.
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